1. Field of the Invention
The invention relates to a manufacturing method of a thin film magnetic head, a manufacturing method of a magnetic recording/reproducing combination head using a magneto-resistance effect type reproducing head and an induction type recording head, a thin film magnetic head and a magnetic recording/reproducing combination head.
2. Description of the Related Art
Responding to recent demand for high densifying of magnetic recording, a high recording density such as 1 Gb/inch.sup.2 is in use in a HDD system. Accompanying such a trend toward the high densification of recording density, a technology capable of giving a narrower track width is indispensable.
For example, in the case of a HDD system possessing a recording density of such as 200 Mb/inch.sup.2, a track width is around 7 .mu.m. Instead, for a HDD system possessing a recording density of 1 Gb/inch.sup.2, a required track width is around 2 .mu.m. To respond a demand for a further higher recording density, a technology capable of giving a narrower track width and higher accuracy is required. In the future, to realize such a high recording density as around 10 Gb/inch.sup.2, a system having a track width narrower than 1 .mu.m is predicted to be demanded.
The structure of a conventional thin film magnetic head which track width is determined by an upper magnetic pole alone, in order to attain above described narrow track width and a high densification of a line recording density, there are problems such as bending at edges of a recording bit line and reproducing riding due to the leakage of magnetic field from sides of a recording track. Thus, the width of the surface opposite to a magnetic gap of a lower portion magnetic pole is necessitated to have the same width as that of the upper magnetic pole.
As methods for giving the same width to both of surfaces facing the magnetic gap between the lower portion magnetic pole and upper portion magnetic pole, following methods can be cited. (1) After transforming beforehand a tip portion of the lower magnetic pole into a convex shape, an upper magnetic pole is mechanically aligned thereon, (2) After forming an upper magnetic pole into a predetermined shape, a lower magnetic pole is milled with an upper magnetic pole as a mask, (3) A lower magnetic pole and an upper magnetic pole are simultaneously processed from an air bearing surface side with such as a FIB (Focused Ion Beam) method.
However, among the above described processing methods, according to the method (1), since a mechanical alignment accuracy due to a stepper is in a range of .+-.0.1 .mu.m, it is difficult to process a narrow track having a width of 1 .mu.m or less with high accuracy. According to the method (2), due to adhesion during milling operation, the track width varies, thus the track width can not be attained with a high accuracy. Further, magnetic short circuit tends to occur between the lower magnetic pole and the upper magnetic pole. According to the method (3), even though a certain degree of the accuracy of the track width can be secured, since each magnetic head is required to be processed one by one and a throughput of the FIB itself is very low, there is a problem when mass-production is required.
A dimensional alignment accuracy between the protruded portions in a butt structure is a universal concerns in processing of various electronic parts not limiting to a magnetic pole structure of a thin film magnetic head. For example, in a case of a semiconductor element, due to finer patterning of a wiring width, there is a growing difficulty in securing the dimensional alignment accuracy when a via hole is aligned on a wiring. Since a via hole is, according to a conventional method, mechanically aligned with an alignment accuracy of around .+-.0.1 .mu.m, precise alignment on the wiring is becoming more and more difficult. The situation is same in a liquid crystal element.
Besides, to cope with the demand for high densification of the line recording density that is described above, a magnetic head (hereinafter referred to as MR head) which makes use of a so-called magneto-resistance effect (MR) is expected as a promising reproducing head, the magneto-resistance effect meaning an electric resistance variation responding to an external magnetic field in a certain type of magnetic thin film or magnetic multi-layer thin film. When a MR head is used as a reproducing head, by forming thereon a recording head consisting of an induction type thin film magnetic head, a magnetic recording/reproducing combination head has been tried to be developed. However, in the magnetic recording/reproducing combination head which integrated a MR head and an induction type magnetic head, due to narrowing of the track width, discrepancy between a reproducing track and a recording track tends to occur.
Further, in a conventional thin film magnetic head, to shield electrically between a magnetic pole and a coil, the coil is covered with an organic insulating material such as resist. Therefore, a distance between a magnetic pole tip portion of an upper portion magnetic pole and a magnetic pole body and a coil can not be made so close. In such a structure, to induce a magnetic field necessary for recording operation on an upper portion magnetic pole, it is required to input a large electric current into the coil. The large electric current can be a cause of disconnection. In order to input large electric current into the coil while preventing the coil from the disconnection, a larger diameter of the coil is required.
In a structure in which a coil is covered with an organic insulating material such as resist, reflecting a rugged shape of the coil, a surface of a substrate on which an upper portion magnetic pole is formed tends to have a rugged shape. An upper portion magnetic pole formed on the rugged shape portion, since a portion reflecting the rugged shape of the substrate works as a pinning site to a domain wall, it is difficult to isolate a magnetic domain. A magnetic pole having multiple domain walls causes to deteriorate magnetic head characteristic, in particular a high frequency response characteristic. In addition, since the organic insulating material such as the resist is less resistant to heat applied for annealing the recording magnetic pole material during head processing stage and heat generated when the electric current is inputted into the coil, reliability of a magnetic head is deteriorated accordingly.
As described above, in a conventional manufacturing method of a thin film magnetic head, a narrow track magnetic head structure, in which width of respective surfaces of the lower portion magnetic pole and the upper portion magnetic pole facing a magnetic gap is same, can not be manufactured with high accuracy while fully satisfying mass productivity. Alignment accuracy in a butt structure between protruded portions is a universal concerns with various types of electronic parts without restricting to a magnetic pole structure of a thin film magnetic head. In addition, in a magnetic recording/reproducing combination head which makes use of a MR head, discrepancy between a reproducing track and a recording track is a growing problem.